1. Field of the Invention
The invention relates to the art of fighting oil well fires whereby these fires can be extinguished by an apparatus which reduces the oil evaporation area and starves the combustible gas with oxygen.
2. Background Art
An oil well fire can be characterized by a burning oil jet issuing from a cylindrical tube which is connected to an underground oil reservoir. Depending on the oil jet velocity, the jet and flame fronts can assume different configurations. The oil burns in a reaction zone surrounding the oil jet which consists of the evaporated oil, air, and evaporating oil droplets. The flame surface separates the reaction zone from the atmosphere and can assume various shapes depending on the laminar (low velocity) or turbulent (high velocity) characteristics of the jet. The higher the oil jet velocity the more intensive will be the mixing between the fuel (oil) and oxidizer (oxygen in the air) and thus more intensive the fire. A burning oil well can thus be viewed as a two-phase flow mixture of oil and gas and can be extinguished if the oxygen or air supply is terminated to the reaction zone. FIG. 1 illustrates schematically a burning oil well fire over which is placed a cylindrical guiding duct 5. As shown in this figure, the radial extent of the flame surface 4 an be controlled if the guiding duct radius R is not very large, since then the flame surface will extend to the wall of the duct and form an underventilated system with the reaction zone 3 enclosed by the oil jet and the duct wall.
To contain the reaction zone or decrease the oil burning rate it is necessary to decrease the area for oil evaporation and the supply of air to the reaction zone. The decrease of surface area for oil evaporation can be accomplished by an inclined plate separator where the oil and gaseous phases are separated from a two-phase mixture. This separator is illustrated in FIG. 2 and consists of an inclined duct 6 which is attached to the guiding duct 5 covering an oil well fire. The purpose of inclining the duct 6 is to take advantage of different inertias of oil and gas. The oil jet and droplets entrained in the gas will have a tendency to travel in a vertical direction due to their large inertias and therefore to strike the upper surface of the duct 6 and flow along this surface. The gaseous phases, consisting of the unburnt air, evaporated fuel, and combustion gases, will be displaced towards the lower surface of the inclined duct 6, and by providing the exit of the duct 6 with a baffle 9 (FIG. 2) the gas stream can be separated from the oil stream. If the air supply at the bottom of the guiding duct 5 is now diminished or eliminated by lowering the apparatus towards the ground 10 and baffle 9 suitably adjusted by closing the gas stream duct 8 it is clear that the fire will be starved of oxygen supply and the fire will be extinguished. Instead of lowering the apparatus towards the ground it is possible to equip the holding duct 5 at the bottom with injectors of neutral gas, such as nitrogen, which will substitute or prevent the air entrainment and thus provide a starvation of oxygen in the reaction zone of the apparatus.